I'm going to asume you are not referring to the optiplex 9010 All-in-One unit. You should be able to upgrade your PSU but it depends upon which size of case you have as to what your power supply size limitations will be. Do you have the mini-tower (MT), Desktop (DT), Small From Factor (SFF) or Ultra Small Form Factor (USFF) case?
That form factor uses a standard ATX PSU, your limitation on the PSU will be the depth - how far back does the current PSU go in and how much additional room do you have behind it before the drives (or cage) interfere?
I would say you shouldn't have any problem going up to a 500W PSU. But I'm going to suggest you find the graphics card that fits your needs and budget and then, armed with that info, decide what size PSU you'll want/need. I'd recommend budgeting about $60-$75 for the PSU.
On your case, does the black door latch seem to prevent the PSU from being more than an inch longer (I can't tell from the pic)
my res now is1024x768 in windowed mode witch is not really bad for me for swtor but i would like it to be more high
That's a really low resolution and that game is not really demanding. Is that the only game you'll be playing? If that's the case the 7770 should be more than enough. If you have a larger screen don't be afraid to increase the resolution and graphics quality with a new video card it should handle it with no problem.
*** Edit: When I asked for resolution I meant the one you're planning on using, ideally your monitor resolution. For best graphics experience you should try to run games at the same resolution as your monitor. What's your monitor resolution? Also, will you be playing other games?
Looking at your picture again, it appears you have a dual lowprofile graphics card setup already which really should be enough for what you seem to want to do (I'm thinking it's the DUAL 1GB AMD RDN HD7470,LP,w/VGA setup they offer). I'm all for upgrades but I don't think you'll get much out of your plan as far as additional performance
My $0.02 here